This invention relates to tetrazoles and more particularly to the metal salts of 5-nitrotetrazole.
Lead azide is one of the most common primary explosives used in detonators. It has been in widespread use for the past 50 years not only in the United States but throughout the world. Despite its almost universal acceptance, its service life is often shortened because of ready hydrolysis in the precence of moisture and carbon dioxide. One of the by-products of hydrolysis is hydrogenazide which in the presence of copper or copper alloys can form various copper azides some of which are even more sensitive, particularly to electrostatic discharge, than lead azide itself. The presence of copper azides is believed to have caused a number of fatal accidents during the handling and storage of munitions, and is also throught to be a factor in premature firings.
Preliminary screening by the British and by the United States Navy indicated that mercuric 5-nitrotetrazole was a promising replacement for lead azide in detonators. Mercuric 5-nitrotetrazole was first reported in 1932 by E. Von Herz in U.S. Pat. No. 2,006,954. He prepared the mercuric 5-nitrotetrazole via the following three step process: ##STR1## In the first step [I], 5-aminotetrazole was reacted with copper sulfate and sodium nitrite in acid solution to produce the acid copper salt of 5-nitrotetrazole. The Von Herz patent gives the following structure for the acid copper salt of 5-nitrotetrazole ##STR2## The second step [II] consisted of using sodium hydroxide to convert the acid copper salt of 5-nitrotetrazole into sodium 5-nitrotetrazole. Finally, in the third step [III], sodium 5-nitrotetrazole was reacted with mercuric nitrate to produce mecuric 5-nitrotetrazole.
During initial experimentation with the von Herz procedure by the U.S. Navy, several problems were encountered. First, during the diazotization there was a continuous series of minor detonations, which while not harmful in themselves, were pschologically disturbing and did on occasion break glassware. Moreover, there was the possibility that the potentially dangerous (in the dry state) acid copper 5-nitrotetrazole salt would be spilled over adjacent surfaces as a result of these detonations. Second, upon completion of the diazotization, the acid copper salt was present as a voluminous gel-like precipitate which required long periods (6 hours or longer) to separate by filtration and to wash free of impurities. This would seriously hamper scale-up operations where large quantities would have to be processed.